Surface chemistry_XII Flashcards by Aliza siawur

Adsorption

Surface phenomenon.

Its the increase in concentration (aggregation) of any molecule at the surface rather than at bulk.

May occur above a ‘solid’ or ‘liquid’ surface. **(not gaseous surface =common sense hai gas pe koi particle kese ruk payega).

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Adsorbent

Solid or liquid surface ON which molecular species are adsorbed.

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Adsorbate

Molecular species which IS adsorbed on the surface.

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Absorption is a _____ phenomenon whereas adsorption is ____ phenomenon.

A’b’sorption = ‘b’ulk phenomenon 
Adsorption = surface phenomenon

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CaCl2 ______water vapours ; silica gel _____ water vapours.

Absorbs/adsorbs

CaCl2 absorbs water vapours ; silica gel adsorbs water vapours.

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Desorption

When molecular species are removed from the surface.

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Occlusion

Adsorption of gas on solid surface.

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Adsorption is _______[exo/endo thermic] process.

Exothermic (heat is released).

Δ H -ve
Δ S -ve (entropy of gas molecules decreases)

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For the process to be spontaneous, magnitude of;
Δ H
Δ G

Δ H > T ΔS i.e ΔG<0 (-ve)

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On increasing temperature, magnitude of T ΔS _____ & ΔG _____.

Magnitude of T ΔS increases whereas |ΔG| decreases

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Select correct statements regarding Physical adsorption (physisorption):

a) not specific.
b) reversible.
c) results in multilayer adsorption
d) not.
c) all of these.

All of these.

It decreases with increase in temperature.

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Physisorption ______ with increase in temperature.

Decreases.

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Chemisorption _______ with increase in temperature.

Increases with increase in surface area.

First increase , attains maximum & then decreases.

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In Freundlich isotherm, value of 1/n & n ranges from?

1/n = 0.1 - 0.5

=> n = 2 - 10

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According to ______theory all adsorption sites are equivalent.

Langmuir isotherm.

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Greater the surafce area _____ is the rate if adsorption.

Greater.

Porous surfaces will show more rate of adsorption.

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KClO3 ———>KCl +3/2 O2

Write the catalyst involved?

MnO2

Temp.= 400-600K

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What’s promotor?

Increases activity of catalyst.

Eg,s MO & K2O are used in Haber’s process as promoter.

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What’s poison?

Decreases activity of catalyst.

Egs., As, Co, Quinoline

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SO2 + ½ O2 ———>SO3

Is an example of ?

Homogeneous catalysis, if catalyst used is NO (g)

Heterogeneous catalysis, if catalyst used in V2O5. [Contact process]

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SO2 + ½ O2 ———>SO3

Is homogeneous catalysis if catalyst is

NO (g)

*reaction/process is called ‘lead chamber process’.

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SO2 + ½ O2 ———>SO3

Is heterogeneous catalysis if catalyst used is

V2O5

*reaction/process is called CONTACT PROCESS .

This is one of 3 MOST IMPORTANT RXNS.

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CH3COOC2H5 + H2O ———>CH3COOH + C2H5OH
Ester. Water. C.acid. Alcohol
whats the catalyst used for this homogeneous catalysis rxn.

H+ (aq.)

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C12H22O11(sucrose/sugar) + H2O ———> C6H12O6 (Glucose) + C6H12O6(fructose)
Catalyst used??

H+ (aq.)

Examples of heterogeneous catalysis?

Contact process: SO2 + ½ O2 ———>SO3 (V2O5 as catalyst) Haber’s process: N2 + 3H2 ———>2NH3 (Fe as catalyst; Mo as promoter) Ostwald’s process: NH3 + O2 ———>NO + H2O (Pt as catalyst) #the 3 most important rxns.

Na2SO3 ———> Na2SO4 | In presence of Na2ArO3 (sod. Arsenate) & O2

Is an example of induced catalysis

Example of auto-catalysis?

MnO4 + C2O4 + H+ ———> Mn+2 + CO2 + H2O Here, Mn+2 produced is used as catalyst for the rxn.

According to modern adsorption, what’s the mechanism of catalysis?

Diffusion>adsorption>reaction>desorption>diffusion.

Zeolites/selective shape catalyst?

Hydrated sodium aluminium silicates. (3D str.)

ZSM-5 a zeolite, acts as catalyst for

Alcohols(R-OH) into gasoline(R-H) i.e dehydrates

1) CO + H2 ———>CH4 + H2O 2) CO + H2 ———>CH3OH 3) CO + H2 ———>HCHO Write catalysts for each of these?

1) CO + H2 ———>CH4 + H2O ; Ni 2) CO + H2 ———>CH3OH ;CuO/ZnO-CH2O3 3) CO + H2 ———>HCHO ; Heat only

Sugar(C6H22O11) +H2O ———> Glucose + fructose | Name the enzyme catalysis?

Invertase.

C6H12O6 ———>C2H5OH + CO2

Zymase.

(C6H12O6)n———> C6H22O11 (maltose)

Diastase.

C12H22O11 + h2o ———> C6H12O6 (glucose)

Maltose.

NH2CONH2 (Urea) + H2O ———>NH3 + CO2

Urease.

Proteins ———>peptides ———>aminoacids

Proteins ———> peptides. ; Pepsin | Peptides ———> amino acids. ;Trypsin

Triglycerides ———>glycerol + fatty acids

Lipase

Activators

Metal ions like Na+ , Mn+2, CO+2

Co-enzymes are ?

Substances which increases activity of enzymes.

Inhibitors destroy the catalytic activity of enzymes. Poisons are substances which slows down activity of enzymes. - both correct -both incorrect - 1st correct - 2nd correct

Both are correct.

Mention particle size in each of these: A) true solution B) colloidal solution C) suspension

A) true solution = less than 10 A° B) colloidal solution = 10-10^4 A° C) suspension = greater 10^4 A°

Adsorption isostere are

Plot at constant x/m b/w pressure and temperature.

``` For adsorption generally ΔH, ΔG, ΔS are: +,-,+ +,-,- -,+,- -,-,-, ```

ΔH -ve ΔG -ve ΔS -ve

In freundlich isotherm, slope of plot of log x/m vs log p gives

Value of 1/n

According to langmuir isotherm, amount of gas adsorbed at very low pressure is

Directly proportional to pressure.

According to langmuir isotherm, amount of gas adsorbed at high pressure is

Independent of pressure as at high pressure x/m is constant.

For langmuir isotherm; Slope of straight line of plot of P/(x/m) vs P graph gives/is

b/a Where b and a are langmuir parameters . Also, the intercept if this graph = 1/a

Ultra filter paper used in ultrafiltration is prepared by

Soaking a filter paper in a colloidal soln. (4% soln. Of nitro cellulose in a mixture of alcohol and ether) hardening by formaldehyde and then dried.

Tyndall effect is not shown by true solutions. | T/F

True

Tyndall effect is due to

Scattering of light by colloidal particles (dispersion phase)

FeCl3 added in excess hot water forms a positively charged sol of hydrated ferric oxide. (T/F)

True. | And a negatively charged sol when FeCl3 is added in NaOH due to adsorption of OH- ions

Electrokinetic potential or zeta potential is?

Difference in potential b/w electrical double layer of opposite charge (called Helmontz electrical double layer) is c/d zeta potential

Coagulating power is inversely proportional to coagulation value. (T/F)

True

Colloidal antimony is used in curing

Kalazaar

_______ sol is used as an eye lotion.

Argyrol in silver sol

Colloidal gold is used for

Intramuscular injection

_______ is an emulsion used for stomach disorder.

Milk of magnesia.

4 methods to coagulate lyophobic colloids?

Electrophoresis By mixing 2 opposite charged sols By boiling By addition of electrolytes